Delayed Job Overwhelming DB - ruby-on-rails-4

Question

I have a method which updates all DNS records for an account with 1 delayed job for each record. There's a lot of workers and queues which is great for getting other jobs done quickly, but this particular job completes quickly and overwhelms the database. Because each job requires DNS to resolve, it's difficult to move this to a process which collects the information then writes once. So I'm instead looking for a way to stagger delayed jobs.
As far as I know, just using sleep(0.1) in the after method should do the trick. I wanted to see if anyone else has specifically dealt with this situation and solved it.
I've created a custom job to test out a few different ideas. Here's some example code:
def update_dns
Account.active.find_each do |account|
account.domains.where('processed IS NULL').find_each do |domain|
begin
Delayed::Job.enqueue StaggerJob.new(self.id)
rescue Exception => e
self.domain_logger.error "Unable to update DNS for #{domain.name} (id=#{domain.id})"
self.domain_logger.error e.message
self.domain_logger.error e.backtrace
end
end
end
end
When a cron job calls Domain.update_dns, the delayed job table floods with tens of thousands of jobs, and the workers start working through them. There's so many workers and queues that even setting the lowest priority overwhelms the database and other requests suffer.
Here's the StaggerJob class:
class StaggerJob < Struct.new(:domain_id)
def perform
domain.fetch_dns_job
end
def enqueue(job)
job.account_id = domain.account_id
job.owner = domain
job.priority = 10 # lowest
job.save
end
def after(job)
# Sleep to avoid overwhelming the DB
sleep(0.1)
end
private
def domain
#domain ||= Domain.find self.domain_id
end
end
This may entirely do the trick, but I wanted to verify if this technique was sensible.

Answer 1

It turned out the priority for these jobs were set to 0 (highest). Setting to 10 (lowest) helped. Sleeping in the job in the after method would work, but there's a better way.
Delayed::Job.enqueue StaggerJob.new(domain.id, :fetch_dns!), run_at: (Time.now + (0.2*counter).seconds) # stagger by 0.2 seconds
This ends up pausing outside the job instead of inside. Better!